JPS5915011B2 - Endothermic reduction method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION It has been known for some time to carry out endothermic reduction processes in so-called rapid or circulating fluidized beds, as can be seen, for example, in Belgian Patent No. 826,521.

Regarding the relationships governing feedstock parameters, gas velocities, etc. to obtain circulating fluidized beds, e.g.
Engineering Progress (Chem, Eng,
Progr.) Vol. 67 No. 2 No. 58-63 (19
71).

The prior art method described above provides a controlled flow of finely divided oxidizing material, finely divided solid and optionally liquid carbon material and molecular oxygen-containing gas to the intermediate section of the zone. maintaining a circulating fluidized bed in an elongated reaction zone while separating gases and solid materials exiting from the upper portion of the reaction zone;
The solid material is recycled to the intermediate section and a portion of the gas stream is introduced into the lower section of the reaction zone as fluidizing and reducing gas after removing dust deposits and most of the CO2 and H20 content and completely Alternatively, the partially reduced substance is discharged from the lower part.

In the prior art process, in order to obtain a high degree of reduction, the height difference between the respective solid material feed and discharge levels must be relatively large.

The reason for this is the need for intense internal circulation of the material in the circulating bed.

Circulating beds, at small altitude differences, result in too much reoxidation of the reducing material in the combustion zone and too short a retention period for some of the oxidizing material in the reduction zone.

These phenomena are hereinafter summarized by the expression "back mixing effect".

It is an object of the invention to substantially reduce said back-mixing effects.

This results in a substantial increase in production per unit volume of reaction zone.

The method of the invention includes a transition zone between the lower and middle sections of the reaction zone and an increase in the velocity of the fluidizing gas in the lower section such that the solid material moves essentially upward in said transition zone. It is characterized by being adapted.

This means that the material in this zone does not circulate within the zone, but is transported through it, thus reducing the backmixing effect.

Said transition zone is therefore hereinafter referred to as transport zone.

Heat transfer from the intermediate section where partial combustion occurs to the lower section of the reaction zone is prevented by the transport zone.

In order to meet the heat demand of the lower zone, the solid material is separated from the mixture of gas and solid material leaving the upper part of the reaction zone, and said solid material is preferably transferred as one or several partial streams to the transport zone. into the lower part of the reaction zone adjacent to.

The invention also includes an apparatus for carrying out the method described above.

According to the invention, the transport zone 4 is designed as a shaft and
comprising a vertically elongated reaction zone enclosed in a furnace space having an upper section 2 connected via an intermediate section 3 to a narrow section acting as a vent and also connected to a lower section 5; The upper part is connected to a separating means 14 which is connected to the lower section 5 via a transport conduit 15 for the separated solid substances and is provided with a gas outlet; An inlet 12.13 for the raw material for the reduction treatment and a nozzle for the molecular oxygen-containing gas are provided, said lower section having at its bottom a nozzle 19 for the reduction gas and a discharge means 20 for the treatment substance. An apparatus for endothermic reduction of finely divided solid materials in a circulating fluidized bed is provided, characterized in that:

The invention will now be described in detail with reference to the drawings, which illustrate the endothermic reduction in a circulating fluidized bed according to the process of the invention and show the apparatus of the invention.

The elongated reaction zone 1 can be considered to consist of the following sections:

namely an upper section 2 for pre-reduction (pre-reduction), an intermediate section 3 for introduction of raw materials and heat generation, a transport zone (the function of which will be explained below) 4 and a lower section 5 for carrying out further reduction.
It is.

The desired increase in the velocity of the fluidizing gas is provided by making the cross-sectional area of the transport zone considerably smaller than that of the lower section of the reaction zone.

In practice it has been found appropriate to increase the gas velocity in the transport zone by a factor of 2 to 6, preferably 3 to 5, compared to the velocity in the lower section of the reaction zone.

Such a speed increase means that essentially all the material entering the transport zone passes through this zone without internal circulation and enters the intermediate section of the reaction zone.

In order to avoid local overheating when the molecular oxygen-containing gas 6 is introduced into the intermediate section 3 and to provide the desired distribution of that gas, this gas supply is placed below the intermediate section 3 adjacent to the transport zone 4. It is further divided into a number of smaller sub-streams 7 at a plurality of separate levels 8 to 11 of the conical section 22 forming the section.

In practice, it has been found that the apex angle α≦45° of the connection section gives a good gas distribution and a low pressure drop.

Carbonaceous material 12 and oxidizing material 13 are also fed into the middle section of this reaction zone, preferably in its upper part.

At its top, the gases and solid substances leaving the upper part 2 of this reaction zone are passed to a separator 14.

The separated solids 15 are returned to the lower section 5, suitably by introduction at 16 of the conical section 23 forming the upper part of the lower section 5 adjacent to the transport zone.

The apex angle β of said conical portion is suitably approximately 90°.

A partial stream 17 of the gas 21 from the separator 14 is removed in a known manner from the main part of its CO2 and H20 content at 18 and is passed to a suitable dispersion means 1 as a reducing gas.
9 into the bottom part of the lower section.

The reduced material is released from the bottom section at 20.

[Brief explanation of the drawing]

The accompanying drawings are detailed illustrations of the invention. 1...Vertical rectangular reaction zone, 2...Upper section, 3...Middle section, 4...Transport zone, 5...Lower section , 6...Molecular oxygen-containing gas, 7...Partial flow, 8-11...
・Level, 12...Carbonaceous material, 13...
・Oxidizing substance, 14...Separator, 15...
・Separated solid, 17...Partial stream, 19...
---Dispersion means.

Claims (1)

Claims: 1. An elongated reaction zone in which the intermediate and lower sections are separated by a transport zone whose gas velocity is high enough to cause essentially all substances entering therein to be transported from the lower section to the intermediate section. an endothermic reduction process in the intermediate section by partial combustion of molecular oxygen in the intermediate section with oxidizing and carbonaceous materials introduced into the section; A portion of the heat generated by partial combustion is transferred to the reaction zone by removing gas and solid material from the upper section and separating the gas from the solid material and introducing the solid material into the lower section. and the partial stream of gas separated from the solid material is utilized for fluidization and reduction in the lower section of the reaction zone after settling of the dust and removal of most of the H2O and CO2 content. A method for carrying out endothermic reduction of finely divided solid materials in a circulating fluidized bed, preferably comprising discharging the reduced material from the bottom of said section. 2 a narrow section designed as a shaft, acting as a transport zone 4 and also connected to the lower section 5 with a gas velocity high enough to transport essentially all the material entering the transport zone from the lower section to the intermediate section; It comprises a vertically elongated reaction zone enclosed in a furnace space with an upper section 2 connected via a section 3, the upper part of said upper section being connected to the separation means 1.
4, the separation means are connected to the lower section 5 via a transport conduit 15 for the separated solid substances and are provided with a gas outlet, and in the upper part of the intermediate section there is a gas outlet for the endothermic reduction treatment. An inlet 12.13 for the raw material and a nozzle for blowing in a molecular oxygen-containing gas are provided, and said lower section is provided at its bottom with a nozzle 19 for blowing in reducing gas and a discharge means 20 for the process substance. Apparatus for the endothermic reduction of finely divided solid substances in a circulating fluidized bed, characterized in that: 3. Device according to claim 2, wherein the intermediate section 3 is tapered conically in the direction of the transport zone 4.